After pondering this a short while, I believe I've experienced 3 types of crushes:
1. Shallow. Usually based on physical attraction, this may result in me looking at her often, but seldom thinking about her outside of that. If her name comes up in conversation, I may listen in just to take in more facts about her. Thinking about her imparts a pleasant feeling to me, although it doesn't go any further than that.
2. Romantic. Usually based on personality compatibility and mutual attraction, this results in me holding a "special place for her" in my heart, so to speak--she is my one, I am exclusive to her and think of no other women. We exchange our desires, thoughts, viewpoints, discuss deep topics as well as shallow topics, laugh together, drive together, etc.
3. Magnetic. Had this maybe 4 times in my life and it's always turned out bad, with one of us diffusing the situation by lack of contact. It tends to happen with EFJ (Fe-dominant) types. Starts out as an intense hands-off chemistry, where I am bitten by the 'bug' but to maintain my facade, I pull back and try not to show my feelings or reveal my thoughts to her, and I deliberately hide my feelings from others, denying them if someone calls me out. I maintain infrequent contact with her, primarily because each encounter, platonic as they might be, are too overwhelming for me to sustain. I idealize her to an obsessive extent, and often lose sleep thinking about her, blind to the fact that I am making things worse by staying out of touch. These begin quickly and die slowly; oftentimes I fantasize about she and I talking or walking together or being in different environments (work, encountering each other at random outside of work, etc.) In my head, a lifetime relationship has already begun and ended by the time we lose contact, months later, when I finally realize we might never speak again. The feelings fade away and I find myself empty for some time, quickly recovering my sense of normalcy.
With romantic relationships I may experience some of the "magnetic" effects for a time (several months), even if they don't start out as such. But women who invoke the "magnetic" crush get that treatment right away.
I am pretty much NT, but I often wonder if I have a bit of NF in my nature too.